Boltzmann-Poisson-like approach to simulating the galactic halo response to satellite accretion Dependence on the halo density profile

Recent studies have reported the detection of the galactic stellar halo wake and dipole triggered by the Large Magellanic Cloud (LMC), mirroring the corresponding response from dark matter (DM). These studies open up the possibility of adding constraints on the global mass distribution of the Milky Way (MW), and even on the nature of DM itself, with current and upcoming stellar surveys reigniting the discussion on response modes in dynamical friction. However, the simulation of such features remains computationally challenging. We used a collisionless Boltzmann equation (CBE)+Poisson solver based on an existing method from the literature. We investigated the density and velocity response modes in simulations of Galactic-type DM halos accreting LMC-sized satellites, including the dependence on the halo density profile. We successfully captured both the local wake and the global over- and underdensity induced in the host halo. We also captured the velocity response. In line with previous studies, we find that the code can reproduce the core formation in the cuspy profile and the satellite core stalling. The angular power spectrum (APS) response is shown to be sensitive to each density profile. The cored Plummer density profile seems the most responsive, displaying a richness of modes. At the end of the simulation, the central halo acquires cylindrical rotation. The CBE description makes it tenable to capture the response modes with a better handling of noise in comparison to traditional N-body simulations. Hence, given a certain noise level, BPM has a lower computational cost than N-body simulations, making it feasible to explore large parameter sets. We anticipate that stellar spheroids in the MW or external galaxies could show central cylindrical rotation if they underwent a massive accretion event. The code can be adjusted to include a variety of DM physics.Comment: 10 pages, 13 figures, Accepted for publication in Astronomy and Astrophysic

The spectrum of the recycled PSR J0437-4715 and its white dwarf companion

We present extensive spectral and photometric observations of the recycled pulsar/white-dwarf binary containing PSR J0437-4715, which we analyzed together with archival X-ray and gamma-ray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum. We find that the optical-infrared part of the spectrum is well fit by a cool white dwarf atmosphere model with pure hydrogen composition. The model atmosphere (Teff = 3950pm150K, log g=6.98pm0.15, R_WD=(1.9pm0.2)e9 cm) fits our spectral data remarkably well for the known mass and distance (M=0.25pm0.02Msun, d=156.3pm1.3pc), yielding the white dwarf age (tau=6.0pm0.5Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25e5 and 3.5e5K. The temperature of the thermal spectrum suggests that some heating mechanism operates throughout the life of the neutron star. The temperature distribution on the neutron star surface is non-uniform. In the X-rays, we confirm the presence of a high-energy tail which is consistent with a continuation of the cut-off power-law component (Gamma=1.56pm0.01, Ecut=1.1pm0.2GeV) that is seen in gamma-rays and perhaps even extends to the near-UV.Comment: 23 pages. To appear in Ap

Lyman-Alpha-Emitting Galaxies at z = 2.1 in ECDF-S: Building Blocks of Typical Present-day Galaxies?

We discovered a sample of 250 Ly-Alpha emitting (LAE) galaxies at z=2.1 in an ultra-deep 3727 A narrow-band MUSYC image of the Extended Chandra Deep Field-South. LAEs were selected to have rest-frame equivalent widths (EW) > 20 A and emission line fluxes > 2.0 x 10^(-17)erg /cm^2/s, after carefully subtracting the continuum contributions from narrow band photometry. The median flux of our sample is 4.2 x 10^(-17)erg/cm^2/s, corresponding to a median Lya luminosity = 1.3 x 10^(42) erg/s at z=2.1. At this flux our sample is > 90% complete. Approximately 4% of the original NB-selected candidates were detected in X-rays by Chandra, and 7% were detected in the rest-frame far-UV by GALEX. At luminosity>1.3 x 10^42 erg/s, the equivalent width distribution is unbiased and is represented by an exponential with scale-length of 83+/-10 A. Above this same luminosity threshold, we find a number density of 1.5+/-0.5 x 10^-3 Mpc^-3. Neither the number density of LAEs nor the scale-length of their EW distribution show significant evolution from z=3 to z=2. We used the rest frame UV luminosity to estimate a median star formation rate of 4 M_(sun) /yr. The median rest frame UV slope, parametrized by B-R, is that typical of dust-free, 0.5-1 Gyr old or moderately dusty, 300-500 Myr old populations. Approximately 40% of the sample occupies the z~2 star-forming galaxy locus in the UVR two color diagram. Clustering analysis reveals that LAEs at z=2.1 have r_0=4.8+/-0.9 Mpc and a bias factor b=1.8+/-0.3. This implies that z=2.1 LAEs reside in dark matter halos with median masses Log(M/M_(sun))=11.5^(+0.4)_(-0.5), which are among of the lowest-mass halos yet probed at this redshift. We used the Sheth-Tormen conditional mass function to study the descendants of these LAEs and found that their typical present-day descendants are local galaxies with L* properties, like the Milky Way.Comment: 35 pages, 9 figures, ApJ, in pres

Program and Proceedings: The Nebraska Academy of Sciences 1880-2010

PROGRAM FRIDAY, APRIL 23, 2010 REGISTRATION FOR ACADEMY, Lobby of Lecture wing, Olin Hall Aeronautics and Space Science, Session A, Olin 249 Aeronautics and Space Science, Session B, Olin 224 Chemistry and Physics, Section A, Chemistry, Olin A Collegiate Academy, Biology Session A, Olin B Collegiate Academy, Chemistry and Physics, Session A, Olin 324 Biological and Medical Sciences, Session A, Olin 112 Biological and Medical Sciences, Session B, Smith Callen Conference Center Chemistry and Physics, Section B, Physics, Planetarium History and Philosophy of Science, Olin 325 Junior Academy, Judges Check-In, Olin 219 Junior Academy, Senior High REGISTRATION, Olin Hall Lobby NWU Health and Sciences Graduate School Fair, Olin and Smith Curtiss Halls Junior Academy, Senior High Competition, Olin 124, Olin 131 Aeronautics and Space Science, Poster Session, Olin 249 Teaching of Science and Math, Olin 325 MAIBEN MEMORIAL LECTURE, OLIN B Dr. Mark Greip, Vice-Chair, Department of Chemistry, University of Nebraska-Lincoln LUNCH, PATIO ROOM, STORY STUDENT CENTER (pay and carry tray through cafeteria line, or pay at NAS registration desk) Aeronautics Group, Conestoga Room Anthropology, Olin 111 Biological and Medical Sciences, Session C, Olin 112 Biological and Medical Sciences, Session D, Smith Callen Conference Center Chemistry and Physics, Section A, Chemistry, Olin A Chemistry and Physics, Section B, Physics, Planetarium Collegiate Academy, Biology Session A, Olin B Collegiate Academy, Biology Session B, Olin 249 Collegiate Academy, Chemistry and Physics, Session A, Olin 324 Junior Academy, Judges Check-In, Olin 219 Junior Academy, Junior High REGISTRATION, Olin Hall Lobby Junior Academy, Senior High Competition, (Final), Olin 110 Earth Science, Olin 224 Junior Academy, Junior High Competition, Olin 124, Olin 131 NJAS Board/Teacher Meeting, Olin 219 Junior Academy, General Awards Presentations, Smith Callen Conference Center BUSINESS MEETING, OLIN B SOCIAL HOUR for Members, Spouses, and Guests First United Methodist Church, 2723 N 50th Street, Lincoln, NE ANNUAL BANQUET and Presentation of Awards and Scholarships First United Methodist Church, 2723 N 50th Street, Lincoln, N

Advanced Geoscience Remote Sensing

Nowadays, advanced remote sensing technology plays tremendous roles to build a quantitative and comprehensive understanding of how the Earth system operates. The advanced remote sensing technology is also used widely to monitor and survey the natural disasters and man-made pollution. Besides, telecommunication is considered as precise advanced remote sensing technology tool. Indeed precise usages of remote sensing and telecommunication without a comprehensive understanding of mathematics and physics. This book has three parts (i) microwave remote sensing applications, (ii) nuclear, geophysics and telecommunication; and (iii) environment remote sensing investigations